When experiencing the issue, I was on my (retina) MacBook Pro disconnected from an external monitor. I had been previously connected to a Dell monitor multiple times between then and my last reboot. Based on some tips I saw online, my first step was a reboot which restored Screeny to normal operation.

To test the “external monitor as cause”, I reconnected to my monitor and tried recording on both screens:

– laptop screen: success
– external monitor: success

Then I disconnected from the external monitor and tried again on just the laptop screen: success.

So I have no idea what happened, or how it got “fixed”, but I recommend trying a reboot if you see this issue.